A smart card is the size and shape of a credit card but has a miniature computer. The miniature computer enables the smart card to perform numerous functions that otherwise could not be performed by a card with a magnetic strip. For example, a smart card may contain user identification data that prohibits unauthorized use. Security is accomplished by using sophisticated cryptographic techniques for communication between the smart card and reading devices. For a general description, see, e.g., "Overview and Applications of Smart Card Technology," at http://www.vitro.bloomington.in.us:8080/2Og4/smrtcard.html; Jose L. Zoreda & Jose Manuel Oton, Smart Cards, (Artech House, Inc. 1994).
A smart card typically contains a Self-Programmable One-Chip Microcomputer (SPOM) with eight metallic metal pads, usually copper, for electronic contact points for communication of data between the smart card and a reading device. The contact points provide power, an input/output for serial data communication, a connection for reading the smart card clock signal, a connection for resetting the smart card, and a connection for the programming voltage of the smart card. Thus, only six of the eight contact points are generally used by present smart cards on the market; the other two are reserved for future use.
The size, function, and location of these contacts are dictated by an industry standard. ISO 7816-2 and 7816-3. This enables the various manufacturers and users of smart cards to create cards and compatible devices to work with the cards.
Smart cards generally contain Random Access Memory (RAM), Read Only Memory (ROM), and Electrically-Erasable Programmable Read Only Memory (EEPROM). The smart card processor typically has an 8-bit data path and 8-bit registers, and the card operates using an operating system selected for the particular application needs.
One aspect of smart cards is the method used for combining the appearance of the card and the need for contact points on the surface. Prior art includes printing verbiage and coloring the contacts with a process that may use either silk screen color or electroplated color. For example, a recently released Mastercard smart card consists of a chip module face with interlocking globes constructed of different contact materials, onto which were added a colored surface to produce letters and image outline.
Another feature of smart card technology is the need to protect the processor from electrostatic discharge (ESD). As the card is carried about, slid into and out of a card holder such as a wallet and slid into card readers, static charges accumulate on the card. When enough charge has accumulated at a particular point on the card, it will attempt to travel to the lowest potential voltage available to it. Typically this lowest potential is ground. If the accumulated charge travels to one of the contact points and through the processor in its attempt to reach a lower potential, the processor will be damaged. This happens because the charge that accumulates can be quite large compared to the maximum voltages and currents the processor is designed to accept. An ESD that travels through a processor is typically large enough to burn or otherwise damage transistors and conductors within the processor such that the processor becomes unoperational after receiving such a charge.